How individual tree characteristics and forest management influence occurrence and richness of tree-related microhabitats in Mediterranean mountain forests

Mediterranean forests are important sources of income for society and represent biodiversity hotspots, characterized by a mosaic of forest structures, from short-rotation even-aged stands to old-growth forests. However, such increased complexity requires forest management to balance timber production with biodiversity conservation at various spatial scales. This study investigated the impacts of forest structures and management alternatives on the occurrence and richness of Tree-related Microhabitats (TreMs) – as proxies for forest biodiversity – in three Mediterranean forests in Italy. The generalized linear mixed model was applied to assess the relationship between a large set of forest structural parameters and the occurrence and richness of TreMs at the tree level, and resulted in an overall model accuracy higher than 80%. The same model was then implemented in hypothetical forest structures, resulting from no management, close-to-nature forestry and combined management system. Results show that at early developmental stages of the stand, no management slightly anticipates the occurrence of TreMs, while in mature forests, the combined forest management system effectively balances forest productivity with biodiversity conservation. The close-to-nature management system is recommended for promoting TreMs richness. Such findings might be used to support sustainable forest management and valorise the multifunctional role of Mediterranean forests.